There's a lot of books about understanding the structure of a screen play through dissecting existing ones. That's the wrong approach, we need to know how to build one from scratch, with the first board. Not what pieces were in a pulled apart house.
If you follow a strict structural approach, you will probably write a well structured bad script.
Structure isn't the dog, it's the tail. It's the symptom of a characters relationship with a central dramatic argument.
We are all of us storytelling machines, it's how we understand our lives. When we narratize our lives we don't think inciding incident, mid act break, etc all that official story structure crap. We think "this happened then this happened." which gets boring, but the good storytellers add "this happened, making me feel this, and that made me realize this about how I'd been approaching things." And that becomes a good story because
"Narration helps us move through a changing world, and story is about a change of state."
there are 3 basic ways a story changes.
1. internal: what is going on inside a character's mind.
2. interpersonal: the main relationship of your story
3. plot: the things going around.
and all of that is made up of scenes. Scenes that follow a Hegelian Dialectic. Each scene has a thesis "this is the truth", and antithesis "no, this is the truth, and here's why" and then the collision and resolution of those into a synthesis, which becomes the next scenes thesis.
Each scene begins with a truth, something happens, and you end with a new truth, that begins the next.
Theme is your central Dramatic Arguement
the dramatic argument doesn't have to be revolutionary, it can be "don't judge a book by it's cover" it's your execution that will be interesting.
but the Theme has to be an argument. Not just "brotherhood" but an actual defensible idea "life is beautiful even amidst horrors"
The purpose of the story is to take your main character, your protagonist, from a place
of ignorance of the truth or the true side of the argument you’re making and take them
all the way to the point where they become the very embodiment of that argument and they
do it through action.
The story starts the character is in a steady balance place, where their life is acceptable though imperfect, and they've achieved it through living the opposite of the theme.
Inciting Incident. The mad god writer throws something at the character that is an ironic disruption of their stasis. A problem that specifically will break their soul, because they have grown broken, so you have to break down so they can regrow in the right way (the way of the theme)
fear is the heart of empathy. The character has lived their life to avoid this thing they fear. The inciting incident is shoving them towards their fear, all they want is to get back to how things were. The audience will empathize with the character trying to protect themself from what they feel vulnerable about, they're afraid of being vulnerable and we all know what that's like.
So you're not thinking of plot, of things that happen. You're thinking of things to prod your character, they spend the 2nd act trying to get back to their anti-theme life. They will experience new things and come out with reaffirmed belief in their antitheme, just making them want to get back to start stronger. But you're also going to introduce a representative of the theme, showing that the antitheme is not the only approach.
Your theme representative and your antiTheme hero will naturally have conflict (which makes good story). But the hero will also be a little attracted to the theme idea, because they are rational.
Midpoint. The hero has a moment of harmony with the theme, either doing it themselves or witnessing it. They see the benefit of the theme, they start having doubt about living antiTheme.
Dramatic Reversal: then you crush them for straying from their antiTheme ways. Inciting incident all over again, worst thing feared happens. Drive them back to antiTheme.
The more you punish, the harder you make it, the more interesting it is, and the sweeter the reward for coming to the light at the end.
Low Point: Crush the hero until they've lost all faith. They don't believe in the antitheme anymore. They don't believe in the theme either, it seems impossible. The goal of getting back to prestory stasis is recognized as insufficient. They're lost.
Defining Moment: character has to do something that proves they accept and believe the new theme. Getting them to a new stasis balance point.
There are no acts. No points to hit. There's just one long story of a character who believes the antiTheme and eventually when faced with lots of hard choices, chooses the path that leads them torturously to belief in the theme.